This is fun to do. Or mess with the pretend law firm that is going to issue an arrest warrant and they have tried to contact you with no results. It's as if I am too stupid to not know how they would send me a legal document. They do not like being questioned.
Or the people with a thick foreign accent saying they are with the government grant department. It's funny how quick they are to say bad words to you like they need more training.
I have heard that you can take the pre paid postage and tape it to a brick. The post office will mail it and the company has to pay by weight. That maybe an urban legend as I know nobody personally that has done this.